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Astron. Astrophys. 351, 413-432 (1999)

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6. Conclusions

We studied the statistics of GLAs with spherically symmetric lens models based on our original X-ray spatial data of all the 15 clusters in the LF94's arc survey sample, obtained by ROSAT HRI . We re-investigated whether the observed number of GLAs in the LF94's cluster sample could be reproduced with the cluster mass distribution models consistent with the X-ray data of spatial distribution of the ICM within a frame work of spherical symmetry assuming isothermality and the hydrodynamical equilibrium. We employed two types of cluster mass distribution models. One is a model comes from the conventional [FORMULA] model used for X-ray spatial data fittings (the `isothermal beta model' in this paper). The other is the universal dark matter halo profile model proposed by NFW (the `ENF98-NFW model' and the `MSS98-NFW model' in this paper). The ENF98-NFW model is a model with the result of cosmological and hydrodynamical simulations to examine the evolution of X-ray emitting hot gas in clusters, by ENF98. The MSS98-NFW model is a model with the result of the theoretical work by MSS98. Models consistent with current best data of spatial distribution of the ICM in the sample clusters taken by ROSAT HRI (isothermal [FORMULA] model and MSS98-NFW model) gave the numbers of GLAs less than two orders of magnitude and this fewness is significant comparing to the uncertainties in the background galaxy model we employed. On the other hand, ENF98-NFW model almost reproduced the observed number of GLAs. Some clusters' virial temperatures of this model, however, are much higher than the temperatures measured by ASCA or evaluated from the [FORMULA] relation of AE98. This indicates that either: non-thermal components of the pressure play a significant role in supporting the ICM (e.g. Loeb & Mao 1994) or the mass distribution of sample clusters deviates significantly from the spherical symmetry. For example, MS1006.0+1202 has straight arcs which cannot be formed by spherically symmetric mass distribution. Some sample clusters show significant irregularity in their X-ray morphologies. We believe that taking into account the irregularity in mass distribution of clusters is therefore very important subject and will constitute the next step together with a better handling of the temperature measurement of the ICM.

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© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999